1. Field of the Invention
This invention relates to an acoustic device that emits repetitive sonic pulses capable of dispersing or incapacitating a biological target. More particularly, a planar array of multiple acoustic pulse sources cooperates to generate highly focused pulses of high intensity sonic energy over a small area.
2. Description of the Related Art
Military and law enforcement personnel have a need for non-lethal weapons. Such weapons are useful in riot control to disperse a hostile crowd. In sniper and hostage situation, a non-lethal weapon provides a means to neutralize a hostile target without collateral damage to hostages, bystanders or property. In combat, a non-lethal weapon is useful to neutralize sentries and warning devices. Since the weapon produces casualties, rather than fatalities, each hit removes three opponents, the injured and a two-person rescue squad, from the combat zone instead of the one person removed by a fatality.
High intensity sound pulses have a debilitating effect on biological targets. Humans become disoriented by exposure to sonic pulses exceeding a threshold of pain of about 150 decibels (dB). Eardrum rupture occurs at about 190 dB, the threshold for pulmonary injury is about 200 dB and the onset of lethality is about 220 dB.
U.S. Pat. No. 3,557,899 to Longinette et al. discloses a parabolic reflector that focuses and transmits a continuous sound at a frequency of between 8 kilohertz (kHz) and 13 kHz. Within this frequency range, sound attenuates rapidly and the disclosed device is believed effective only at close ranges. The U.S. Pat. No. 3,557,889 patent discloses utilizing the device in close proximity to a riot or in enclosed areas, such as a bank vault.
U.S. Pat. No. 4,349,898 to Drewes et al. discloses a sonic weapon to destroy buildings and disable personnel. A plurality of tubes each conduct a continuous sound generated by a jet engine. Rotating fans at the ends of the tubes create pulsed sound of a desired frequency. The fan speeds are set such that each tube has a pulse sound frequency two times the frequency of a preceding tube leading to an additive effect of sound waves referred to as a parametric pump. The disclosed device appears heavy and requires careful alignment of a number of large apparatus for operation.
There remains, therefore, a need for a portable acoustic weapon capable of dispersing or disabling biological targets at distances of up to 100 meters that does not suffer from the disadvantages of the prior art discussed above.